/*
 *                               POK header
 *
 * The following file is a part of the POK project. Any modification should
 * be made according to the POK licence. You CANNOT use this file or a part
 * of a file for your own project.
 *
 * For more information on the POK licence, please see our LICENCE FILE
 *
 * Please follow the coding guidelines described in doc/CODING_GUIDELINES
 *
 *                                      Copyright (c) 2007-2021 POK team
 */

/* @(#)s_asinh.c 5.1 93/09/24 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

/* asinh(x)
 * Method :
 *	Based on
 *		asinh(x) = sign(x) * log [ |x| + sqrt(x*x+1) ]
 *	we have
 *	asinh(x) := x  if  1+x*x=1,
 *		 := sign(x)*(log(x)+ln2)) for large |x|, else
 *		 := sign(x)*log(2|x|+1/(|x|+sqrt(x*x+1))) if|x|>2, else
 *		 := sign(x)*log1p(|x| + x^2/(1 + sqrt(1+x^2)))
 */

#ifdef POK_NEEDS_LIBMATH

#include "math_private.h"
#include <libm.h>
#include <types.h>

static const double one =
                        1.00000000000000000000e+00, /* 0x3FF00000, 0x00000000 */
    ln2 = 6.93147180559945286227e-01,               /* 0x3FE62E42, 0xFEFA39EF */
    huge = 1.00000000000000000000e+300;

double asinh(double x) {
  double t, w;
  int32_t hx, ix;
  GET_HIGH_WORD(hx, x);
  ix = hx & 0x7fffffff;
  if (ix >= 0x7ff00000)
    return x + x;        /* x is inf or NaN */
  if (ix < 0x3e300000) { /* |x|<2**-28 */
    if (huge + x > one)
      return x; /* return x inexact except 0 */
  }
  if (ix > 0x41b00000) { /* |x| > 2**28 */
    w = __ieee754_log(fabs(x)) + ln2;
  } else if (ix > 0x40000000) { /* 2**28 > |x| > 2.0 */
    t = fabs(x);
    w = __ieee754_log(2.0 * t + one / (__ieee754_sqrt(x * x + one) + t));
  } else { /* 2.0 > |x| > 2**-28 */
    t = x * x;
    w = log1p(fabs(x) + t / (one + __ieee754_sqrt(one + t)));
  }
  if (hx > 0)
    return w;
  else
    return -w;
}

#endif
